ATP, P2X2, and P2X3 in human HNSCC microenvironment and pain. a. Representative HPLC chromatograms showing ATP peaks from tumor and matched normal tissue harvested from the same patient. b. Tumor tissues (Ipsi) had higher levels of ATP compared to matched normal sites (Contra) (n = 10, Student’s t-test). c. Pain scores of functional sharpness and intensity were significantly higher than spontaneous sharpness and intensity, respectively (n = 13, Student’s t-test). d. Mean scores of functional pain (Q2, 4, 6, 7, 8) were significantly higher than spontaneous pain (Q1, 3, 5) (Student’s t-test). e. ATP concentration in extracted cancer tissue correlated positively with mean pain scores (linear regression). f. Representative H&E and immunofluorescence staining (P2X2, P2X3, merged) of a human tongue SCC. Sections were taken from adjacent sections of the SCC. Scale bar: 100 μm.